This invention relates generally to easy opening containers and more specifically to easy opening containers of the ecology type having a nondiscardable tear strip.
The ready acceptance of easy opening containers has resulted in extensive use of this type of container for a substantial number of products, especially comestible products such as beverages including beer, soft drinks, and the like. A common variety of this type of container is characterized by a lever or tab permanently joined to a tear strip, the latter being separable from the container to provide a pouring spout in the end wall of the container. With this common type of pull tab container, the tear strip and the tab have been entirely removable and discardable.
The convenience of easy opening containers has created problems due to the unfortunate and indiscriminate disposition of the severed portion of the container. For example, beach and picnic areas have had an accumulation of litter in the form of tabs and tear strips which have been removed from easy opening containers. These discarded tabs and tear strips are quite difficult to clean up because they are small and therefore pass through the tines of any raking apparatus. Being normally made of aluminum, they cannot be collected by magnetic means. Nonetheless, this type of container is widely used.
In addition to the problem of litter, the widespread use of easy opening containers has increased the incidence of laceration due to exposure of the free edge formed after the score line is ruptured and the tear strip removed.
There also have been problems associated with the accidental rupturing of the weakened area of the score line. These problems have typically occurred during shipping where several of the containers have been stacked, thereby producing significant stacking forces on the weakened areas. This problem has been further compounded by the provision of finger tabs of the type having a projection adjacent to the score line which localizes pressure on the score line when the tab is lifted. Although this type of finger tab has been desirable to facilitate opening of the container, mere stacking pressures on this type of tab have often resulted in the accidental rupturing of the score line.
Several different approaches have been used in the prior art to overcome some of the foregoing problems. By way of example, the noncontinuous score line has been used such that the tear strip remains attached to the container; see, for example, U.S. Pat. No. 3,327,891. An improvement in the structure described in the aforementioned U.S. Patent is set forth in U.S. application Ser. No. 103,255, filed Dec. 31, 1970, and assigned to the same assignee. In this application, a container end having an inseparable tear strip is described as including means to eliminate sharp edges along the score line. Another improved approach to the problem is described in U.S. Patent application Ser. No. 346,712, filed Mar. 30, 1973, and assigned to the same assignee.
Recently, container ends have been formed with what is described as a "push-button end" in that buttons are formed in the end wall. One such structure is illustrated in U.S. Pat. No. 3,334,775 in which a panel is forced downwardly into the container for providing a pour opening. In that structure, the score line is so formed that the score faces the interior of the container, i.e. the "non-public" side, so-called. The score is in turn covered by a plastisol sealant which is positioned on the underside i.e. the interior or non-public side of the container. In the usual course, the container end is fabricated and then the plastisol is applied. Not only is the application of a plastisol or other coating to a fabricated container end a relatively expensive operation, but there are other objections.
For example, in opening such a container the panel is forced into the container and the sealant bead must be ruptured. If the bead does not rupture "clean" small pieces of the sealant may separate and fall into the container. In other cases, "stringers" are formed. It is apparent that formulation of the sealant must be such as to avoid ingredients which may adversely affect the flavor of the product within the container. Also, harmful components which may be extracted from the sealant must be avoided.
Yet, when the score line is on the non-public side of the end wall, a sealant or other protective coating is used.
Another type of push-button end currently being used involves a lanced panel which forms a hinged opening panel. The lanced panel is thereafter coined such that its radial dimension is greater than that of the opening. The lanced panel is then sealed to the end wall by a bead of sealant placed on the non-public side of the end wall, and giving rise to the same objections noted above.
The normal procedure for opening a container having a push-button end involves manually forcing the button into the container by use of one's finger, as opposed to the use of an integrally attached tab to pull the button upwardly and away from the end wall, as is the case with the tear strip type of easy open containers. By forcing the button downwardly into the container, either as a separately severed element which drops into the container, or as a hinged panel which is bent toward the underside of the end wall, the problem of loose pieces which could be considered a source of litter is overcome. However, a potential hazard exists because of the free edge of the score line which results and the necessity for the user to urge the panel down into the container thus necessitating positioning of one's finger in close proximity to the free edge of the score.
Structures for end walls of containers are also known in which protective beads are formed to protect against laceration. For example, see U.S. Pat. No. 3,303,958 which describes an end wall which is removed by pulling away from the container. U.S. Pat. No. 3,696,961 describes an end in which the end wall is bent downwardly to rupture the score line and then the panel is pulled outwardly as a separate piece. Again, the use of a plastisol sealant is described.
U.S. Pat. No. 3,362,569 of 1968 describes a variant of a push button type of convenient opening. Somewhat modified in form, the type of score line there described has been used for push button ends and is referred to as a "pinched" score line.
In a U.S. Pat. Application Ser. No. 413,842 assigned to the assignee of the present application, an easy open push button ecology end is disclosed which includes protective means cooperating with a push button panel of an end wall. The protective means overlies the panel and the score line to prevent contact between the free edge of the score line and the user and to prevent the panel from being withdrawn through the formed aperture in the end wall. The portions of the end wall which are connected to the side wall of the container are disposed in a different plate than the panel of the end wall so that a shoulder is formed. This shoulder supports the annular protective means in proximity to the score line.